Damage sensitivity of dental zirconias to simulated occlusal contact. Issue 1 (January 2021)

• Record Type: Journal Article
• Authors: Borba, Marcia; Okamoto, Tomoyuki K.; Zou, Michelle; Kaizer, Marina R.; Zhang, Yu
• Is Part Of: Dental materials. Volume 37:Issue 1(2021)
• Page Start: 158
• Page End: 167
• Publication Date: 2021-01
• Subjects: Ceramics -- Prostheses -- Mechanical damage -- Strength degradation -- Sliding contact -- Occlusion; Dentistry -- Periodicals; Dental materials -- Periodicals; 617.695
• DOI: 10.1016/j.dental.2020.10.019
• Languages: English
• ISSNs: 0109-5641

Abstract

Graphical abstract: Highlights: Laboratory sliding sphere tests simulate essential features of occlusal contact. At P = 200 N, strength degradation in 3Y- and 5Y-PSZ occurs after <50 sliding cycles. At P = 50 N, strength degradation in both zirconias occurs after 750–1000 sliding. After the first falloff, further occlusal loading only moderately lowers the strength. A 50-N occlusal load can debase the strength of zirconia as much as a 200-N load. Abstract: Objective: Mechanical damages can occur from dental restoration processing and fitting, or while it is in-service. This study evaluates the damage sensitivity of translucent zirconia (5Y-PSZ) relative to conventional 3Y-PSZ following mouth-motion simulations at various loads. Methods: 5Y-PSZ and 3Y-PSZ discs were adhesively bonded to a dentin-like substrate and divided into groups according to the load (50 N or 200 N) and number of cycles (up to 10 6 ) used in the chewing simulation. Specimens were mounted with 30° inclination in an electrodynamic mouth-motion simulator, and subjected to contact-slide-liftoff cyclic loading in water. Surface and sub-surface damages were analyzed using a sectioning technique. After the simulation, specimens were removed from the substrate and loaded with the damaged surface in tension for biaxial strength testing to assess their damage tolerance. Results: The strength of both ceramics underwent significant degradation after mouth-motion simulations. For 5Y-PSZ, the strength degradation was greater (∼60%) and occurred at a lower number of cycles than 3Y-PSZ. Herringbone cracks emerged on 3Y-PSZ and 5Y-PSZ surfaces under a 200-N load after 50 and 10 cycles, respectively. Meanwhile at a 50-N load, cracks formed at ∼1000 cycles in both ceramics. Further increasing the number of cycles only had moderate effects on the strength of both ceramics, despite an increase in surface and sub-surface damage. More significantly, a 50-N occlusal load can debase the zirconia strengths as much as a 200-N load. Significance: Surface flaws produced during the chewing simulation are capable of significant strength degradation in zirconia, even after a small number of low-load cycles.